linux-kernel - [PATCH 03/23] vfs: define usercopy region in names

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Message-Id: <1497915397-93805-4-git-send-email-keescook@chromium.org>
Date:   Mon, 19 Jun 2017 16:36:17 -0700
From:   Kees Cook <keescook@...omium.org>
To:     kernel-hardening@...ts.openwall.com
Cc:     Kees Cook <keescook@...omium.org>,
        David Windsor <dave@...lcore.net>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 03/23] vfs: define usercopy region in names_cache slab caches

From: David Windsor <dave@...lcore.net>

vfs pathnames stored internally in inodes and contained in
the names_cache slab cache need to be copied to/from userspace.

In support of usercopy hardening, this patch defines the entire
cache object in the names_cache slab cache as whitelisted, since
it holds name strings to be copied to userspace.

This patch is verbatim from Brad Spengler/PaX Team's PAX_USERCOPY
whitelisting code in the last public patch of grsecurity/PaX based on my
understanding of the code. Changes or omissions from the original code are
mine and don't reflect the original grsecurity/PaX code.

Signed-off-by: David Windsor <dave@...lcore.net>
[kees: adjust commit log]
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/dcache.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index cddf39777835..f7f3c4114baa 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3616,8 +3616,8 @@ void __init vfs_caches_init_early(void)

 void __init vfs_caches_init(void)
 {
-	names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
-			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
+	names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
+			SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL);

 	dcache_init();
 	inode_init();
-- 
2.7.4